/*
 * Copyright 2017-2019 The OpenTracing Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package io.opentracing.contrib.grpc;

import io.opentracing.SpanContext;

/** An interface that defines how to get the current active span context. */
public interface ActiveSpanContextSource {

  /** ActiveSpanContextSource implementation that always returns null as the active span context. */
  ActiveSpanContextSource NONE =
      new ActiveSpanContextSource() {
        @Override
        public SpanContext getActiveSpanContext() {
          return null;
        }
      };

  /**
   * ActiveSpanContextSource implementation that returns the current span context stored in the GRPC
   * context under {@link OpenTracingContextKey}.
   */
  ActiveSpanContextSource GRPC_CONTEXT =
      new ActiveSpanContextSource() {
        @Override
        public SpanContext getActiveSpanContext() {
          return OpenTracingContextKey.activeSpanContext();
        }
      };

  /**
   * Retrieves the active {@link SpanContext}.
   *
   * @return the active span context
   */
  SpanContext getActiveSpanContext();
}
